As one of the most successful technical innovations in history, mobile communication develops extremely rapidly. With gradual increase of mobile users, mobile applications, and mobile services, a requirement of large-capacity, low-delay, and more reliable mobile communication also gradually increases. In recent years, the foregoing requirement is partly met by using more advanced communications technologies, allocating more spectrums, and deploying denser base stations. However, mobile data services are to present an explosive growth trend in the next decade according to a forecast, which poses a more severe challenge to design of a next generation mobile communications network. Currently, most of low-band spectrum resources (for example, bands below 3 GHz) that are applicable to mobile communication are already allocated. However, a large quantity of spectrum resources in a band between 3 GHz and 300 GHz are still not allocated or used. According to a definition from ITU, a band between 3 GHz and 30 GHz is referred to as a super high frequency (SHF) band, and a band between 30 GHz and 300 GHz is referred to as an extremely high frequency (EHF) band. The SHF band and the EHF band have a similar propagation characteristic (a relatively large propagation loss) and a wavelength range between 1 millimeter and 100 millimeters, and therefore a band between 3 GHz and 300 GHz is collectively referred to as a millimeter-wave band.
However, research on using the millimeter-wave band in cellular mobile communication is still in an initial stage, and a technology is still not mature. When accessing a millimeter-wave band network, user equipment needs to acquire a PSS in a PSS (English: Primary Synchronization Signal) synchronization window that slides in the millimeter-wave band for a long time, and synchronization in the millimeter-wave band cannot be accelerated. For example, as shown in FIG. 1, in an actual transmission process, when a user receives a cellular band frame and a millimeter-wave band frame, a delay is to be generated between start locations of the cellular band frame and the millimeter-wave band frame. The delay is caused by various factors, for example, a transmit delay difference in a cellular band and the millimeter-wave band on a base station side, a delay difference caused by a millimeter-wave band RF (English: Radio Frequency) channel device and a cellular band RF channel device, and a delay difference caused by different space propagation paths of different band signals.